Aspects of immunoglobulin replacement therapy

Immunoglobulin replacement therapy appears to benefit some patients who have IgG subclass deficiencies. Because some patients with subnormal trough concentrations of IgG subclasses remain well, because other patients who have borderline/low normal concentrations of an IgG subclass are abnormally infection-prone and helped by immunoglobulin therapy and because infection proneness in individual patients does not always appear to parallel their IgG subclass concentrations, it is evident that IgG subclass concentrations, while a helpful guide, are not an absolute determinant of the need for immunoglobulin replacement therapy in infection-prone patients. Low IgG subclass concentrations may indicate impaired ability to produce certain "specific" antibodies and antibody replacement is likely to be the crucial factor in treatment rather than merely maintaining concentrations of IgG subclasses at particular levels.